This invention relates generally to a system combining a heat exchange unit including a water tank with a compressor-type refrigerator in a manner whereby energy for heating cold water conducted through the unit is extracted from the refrigerator, and more particularly to a thermally-integrated system of this type in which the heat dissipated by the refrigerator unit is fully exploited, yet its efficiency is maintained despite changing temperature conditions in the water tank.
There are many facilities which require a compressor-type refrigerator as well as running hot water. Thus the typical restaurant must have one or more refrigerators in which to refrigerate vegetables, meats and liquids, and it must also have a hot water supply to carry out various cleaning operations.
In the usual restaurant installation, an electrically energized compressor-type refrigerator is operated in a manner totally independent of the hot water supply, as a consequence of which heat removed in the condensing process is wasted. And where the removed heat is not discharged through an exterior vent but into the refrigerator area, this heat may impose an additional load on an air conditioning system operating in that area. On the other hand, hot water is supplied by conventional water heaters operated by gas, oil, or electrical energy. Where the demand for heated water is high, the energy costs therefor are substantial.
The concept of extracting heat from a refrigerator for the purpose of heating the water in a water heater is well known in the art. Thus in the 1979 U.S. Pat. to Amthor, Jr., No. 4,173,872, the condenser coil of a refrigerator is disposed within a water tank and serves to raise the temperature of the water therein. Arrangements along similar lines are disclosed in the patents to Hammell, U.S. Pat. Nos, 2,668,402; Johnson, 4,178,769; Mueller, 4,146,089 and Eggleston, 2,125,842.
While the arrangements disclosed in these prior patents serve to utilize otherwise wasted energy, they fail to fully and effectively exploit the available heat energy and make no adequate provision to maintain efficient operation of the refrigerator under optimum conditions regardless of the changing demand for hot water normally experienced in a restaurant or similar facility.
For example, if the condenser coil of the refrigerator is disposed within the water tank in heat exchange relation with the water therein, and no water is withdrawn from the tank for a prolonged period, the rising temperature of the water in the tank will approach the temperature of the refrigerant passing through the coil. As a consequence, a proper condensing action will not take place, causing the refrigerator to automatically cut off.
If, on the other hand, heated water is continuously drawn from the water tank so that the temperature of the water in the tank begins to approach the relatively low temperature of incoming water replenishing the water withdrawn from the tank, then an excessive condensing action will take place that will interfere with the proper operation of the refrigeration unit.
In the copending application Ser. No. 141,265, filed May 5, 1980 of Baumgarten et al., whose entire disclosure is incorporated herein by reference, a system is disclosed for combining a water heater tank with a refrigerator whereby energy for heating the water is extracted from the refrigerator, yet the efficiency of the refrigerator is maintained despite changing temperature conditions in the water tank.
In this system, an external line conveying the hot refrigerant and acting as an auxiliary condenser is extended from the compressor of the refrigerator to the main condenser thereof, the external line first passing through the upper region of the tank where it serves in conjunction with a water jacket interposed in the tank outlet pipe as a heat booster. The external line then runs through the lower region of the tank in a coiled formation in heat exchange relation with relatively-cold pressurized incoming water supplied by an inlet pipe, whereby the water heated thereby flows by convection toward the upper region of the tank where the temperature thereof is boosted as the water is discharged through the outlet pipe.
Automatic control means act to divide the condensation function of the refrigerator between the auxiliary and main condensers in response to changing temperature conditions in the water tank, the condensation action of the main condenser being increased when the water in the tank is at a high temperature.
Because of certain code regulations, a system of the type disclosed in our copending application may not be acceptable in some municipalities. The reason for this is that hot water derived from the tank and used for cleaning purposes may become contaminated should a leak develop in the external line passing through the tank. Since this line carries a refrigerant such as Freon intermingled with some lubricating oil from the compressor, a rupture in the external line will introduce the refrigerant and the lubricating oil into the tank water and thereby render the hot water supply impure.